In the process of establishing an oil or gas well, the well is typically provided with an arrangement for selectively excluding fluid communication with certain zones in the formation to avoid communication with undesirable fluids. A typical method of controlling the zones with which the well is in fluid communication is by running well casing down into the well and then sealing the annulus between the exterior of the casing and the walls of the wellbore with cement. Thereafter, the well casing and cement may be perforated at preselected locations by a perforating device or the like to establish a plurality of fluid conduits between the pipe and the product bearing zones in the formation. Unfortunately, the process of perforating through the casing and then through the layer of cement dissipates a substantial portion of the energy from the perforating device and the formation receives only a minor portion of the perforating energy.
As is known in the art, perforating the formation may significantly enhance the percentage of hydrocarbons that may be extracted from a well. Accordingly, the well is worked over several times during its producing life to enlarge the fractures in the producing zone permitting a larger percentage of the hydrocarbons in the formation to be produced. Typical procedures for enlarging or creating fractures are by acid treatments or by the application of significant hydraulic pressure. The hydraulic pressure is typically performed when the well is established since the equipment for generating the pressure is at the site.
Accordingly, it is an object of the present invention to provide a method and apparatus for perforating the formation in a wellbore which overcomes or avoids the above noted limitations and disadvantages of the prior art.
It is a further object of the present invention to provide a method and apparatus for perforating a wellbore which remains within the profile of the pipe while the pipe is moved into and around the wellbore.